SEOUL, South Korea — North Korea appeared on Tuesday to pause its threat to launch ballistic missiles toward Guam, saying it would wait to assess “the foolish and stupid conduct” of the United States before carrying the launchings out.

The statement came as the United States and South Korea were preparing to conduct joint military exercises on the Korean Peninsula and surrounding waters starting on Monday, despite North Korea’s vehement opposition to such drills.

In response to threats from President Trump, North Korea’s military announced last week that by mid-August, it would submit a plan to Kim Jong-un, the country’s leader, for launching four ballistic missiles into waters around Guam, the United States territory that is home to American military bases.

On Monday, Mr. Kim reviewed the plan while visiting the command of the Strategic Force of the Korean People’s Army but said he would wait a bit before telling the military to proceed with the missile launchings, the state news media reported on Tuesday.

“He said that the U.S. imperialists caught the noose around their necks due to their reckless military confrontation racket, adding that they would watch a little more the foolish and stupid conduct of the Yankees,” said the report from the Korean Central News Agency.

Mr. Kim’s decision to wait “a little more” before ordering the launchings represented a slight ratcheting down of tensions and came after some of Mr. Trump’s top aides on Monday tried to tamp down fears of a clash after his threat to rain “fire and fury” on North Korea.

South Korea’s president, Moon Jae-in, on Tuesday offered an unusually blunt rebuke to the Trump administration’s discussions of possible military responses to the North, saying no country should take military action on the Korean Peninsula without his government’s approval.

“It’s only South Korea that can decide on a military action on the Korean Peninsula,” Mr. Moon said during a nationally televised speech marking National Liberation Day, which celebrates the end of Japanese colonial rule of Korea at the end of World War II. “No one should be allowed to decide on a military action on the Korean Peninsula without South Korean agreement.”

South Koreans have grown increasingly concerned in recent days about a possible military conflict following Mr. Trump’s threats against the North.

As the exchange of combative rhetoric intensified between Mr. Trump and Mr. Kim, Mr. Moon and his office have issued a steady stream of statements opposing any armed conflict on the peninsula.

Although Mr. Moon’s latest statement did not mention Mr. Trump by name, it marked his strongest expression of disapproval of military options being considered by Washington.

In a meeting with Mr. Moon on Monday, Gen. Joseph F. Dunford Jr., the chairman of the Joint Chiefs of Staff, agreed with the South Korean leader that the standoff over North Korea’s nuclear and missile threats should be resolved through diplomacy and sanctions. But the top American general added that the United States was preparing military options in case those efforts failed.

“The United States military’s priority is to support our government’s efforts to achieve the denuclearization of the Korean Peninsula through diplomatic and economic pressure,” General Dunford was quoted as saying in a Korean-language statement released by Mr. Moon’s office after the meeting on Monday. “We are preparing a military option in case such efforts fail.”

On Tuesday, General Dunford met in Beijing with his Chinese counterpart, Gen. Fang Fenghui, discussing North Korea, as well as Taiwan and the South China Sea. It was not clear what message General Dunford delivered, or whether the generals discussed China’s proposal that North Korea freeze its nuclear testing in exchange for the United States cutting sharply back on its military exercises with South Korea.

The Pentagon and the State Department have said in the last several days that the Trump administration favors diplomacy to resolve the North’s nuclear expansion, but they have rejected China’s proposal, which it first presented earlier this year.

In a statement after the meeting, General Fang struck a conciliatory tone on the relationship between the United States and China, but made no mention of North Korea. “Cooperation is the only right choice between China and the U.S.,” he said.

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A rally against the United States outside an American Army base in Seoul on Monday.CreditJung Yeon-Je/Agence France-Presse — Getty Images

In his speech on Tuesday, Mr. Moon said that his government would “do everything it can to prevent war.” At the same time, he called for dialogue with North Korea, repeating his long-held belief that sanctions alone cannot solve the crisis over North Korea’s nuclear weapons and missile programs.

“The purpose of strong sanctions and pressure against North Korea is to bring it to the negotiating table, not to raise military tensions,” he said.

The South Korean leader urged North Korea to help create momentum toward dialogue by not conducting any more nuclear or missile tests.

He also reiterated his proposal to the North that the two Koreas organize reunions of families separated during the 1950-53 Korean War as a first step toward easing tensions and improving ties on the divided Korean Peninsula.

China and Russia also kept up pressure on North Korea and the United States to tone down the language of their exchanges. The Chinese foreign minister, Wang Yi, told his Russian counterpart, Sergey V. Lavrov, in a phone call on Tuesday that their governments should “not permit anyone to provoke incidents at the doorsteps of China and Russia,” according to the Chinese Foreign Ministry.

“The urgent task is to slam the breaks on the mutually provocative words and actions between North Korea and the United States,” Mr. Wang said. “Cool the tensions and prevent an ‘August crisis’ from breaking out.”

Mr. Trump held a 30-minute call on Tuesday with Shinzo Abe, Japan’s prime minister, about the tensions in the region.

In comments to reporters Tuesday morning Japan time, Mr. Abe said that the two leaders “frankly exchanged opinions on the current North Korean situation,” saying he appreciated Mr. Trump’s “commitment to the safety of its allies.”

Mr. Abe, who has emerged as one of Mr. Trump’s most loyal allies, said that he and Mr. Trump “shared the view that the priority is not to let North Korea launch missiles.”

Motoko Rich contributed reporting from Tokyo, and Jane Perlez and Chris Buckley from Beijing. Adam Wu contributed research from Beijing.